The present invention is directed to a valve operator for providing a quarter turn to a valve. Many valves, such as ball, plug or other stem-mounted valves, operate with one-quarter turn between a full open and a full closed position. On small valves, very little force is required. On large valves, opening against significant pressure levels, very substantial torque is required to open or close the valve. The present invention is directed to a valve operator which can provide substantial torque. Yet, the valve operator is easily installed so that only one-quarter of a revolution is delivered. Heretofore, hydraulic or pneumatic valve actuators have utilized a piston and cylinder arrangement where the piston is connected to a piston rod, and the piston rod, in turn, rotates an eccentric arm via a clevis connection. With such a typical installation, there are difficulties in scaling the linear stroke of the piston and cylinder arrangement to the dimensions of the eccentric whereby ninety degrees (90.degree.) of rotation is achieved at the stem. The present invention overcomes these difficulties. It provides a valve operator adapted to be connected to a quarter turn valve and, in particular, enables in line connection between the valve stem and the rotatable shaft of the operator. Such an arrangement is compact and avoids exposed eccentric arms and the like. This, of course, increases operator safety and reduces the chance of foreign devices becoming entangled to the detriment of safety and reliability.
The present invention is a fluid powered valve actuator. Fluid power is quite often readily available at a given installation. Fluid power is easily adapted for the present invention by providing a valve which delivers the fluid power to the fluid actuated operator. When fluid is delivered, it drives the actuator to one extreme or the other of its movement. Fortunately, the device is constructed and arranged so that only one-quarter of a revolution is provided. This is advantageous because there is no need to construct external limit switches, stops or motion limiting devices which restrain the stroke of the equipment to one-quarter turn. Accordingly, the only thing which is exposed in the present apparatus is the central shaft in the valve actuator, and this enables the valve to be connected at either end. The other end is left exposed as desired, and it can be capped if necessary. This is highly convenient and provides extremely safe equipment with almost no exposed moving parts.
The present invention is particularly adapted to be used with a pneumatic power source. Pneumatic power at a specified pressure is applied through a control valve to the fluid actuated device. In the event that significant resistance is encountered, pressure builds up internally in the actuator and achieves a level sufficient to drive the actuator. As the pressure build-up is achieved, the device responds to operate the connected valve. Such an operation is achieved by applying torque to the valve to be rotated, the measure of torque being proportionate to the pressure applied to the actuator.